Petri

Petri is a game for Android. The basic goal is to grow a cell culture in a Petri dish. Challenges include fending off undesirable species of cells, fending off viral phage infections, and directing the evolution of the cell culture toward various traits such as radiation-resistence or a preference for cold or hot temperatures.

The primary tools are a set of lasers criss-crossing the dish which can be activated to heat portions of the dish and kill the cells. Secondary tools let you place new cell cultures, add agar to speed up cell growth, infect bad cells with phages, irradiate the dish, grow penicillium colonies, and pour puddles of sterilizing bleach on the dish. There is also a thermostat which permits you to control the temperature.

During gameplay occasional power-ups appear which, when obtained by placing them in the cross-hairs of the lasers, either increase your tool supply, add additional lasers, or add point bonuses. The levels are grouped into stages which correspond to difficulty, with each stage consisting of several individual rounds in which each round has slightly different properties such as end-condition and motivating point bonuses (goals for the round in effect).

Games are automatically saved between rounds and can be loaded at a later time. Scores are automatically saved to a scoreboard and are also submitted to a global scoreboard to compete with players all over the world. While the game is free to install, there are various in-app purchases available. First, it is possible to upgrade the app to allow more lost rounds per game before the game ends, thus enabling a higher final score. Second, it is possible to purchase 'replays' which can be used to retry lost rounds in an attempt to extend games which have otherwise ended.